Structural analysis of Sr8Ga16Ge30 clathrate compound
Structural analysis of Sr8Ga16Ge30 clathrate compound
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Sr8Ga16Ge30笼形化合物的结构分析
DOI：
10.1063/1.372044
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发表时间：
2000
影响因子：
3.2
通讯作者：
S. Hwu
中科院分区：
文献类型：
--
作者：
S. Schujman;G. Nolas;R. Young;Cora Lind;A. Wilkinson;G. Slack;R. Patschke;M. Kanatzidis;M. Ulutagay;S. Hwu
利用x射线粉末衍射数据，采用Rietveld细化方法对Sr8Ga16Ge30化合物进行了晶体结构表征。该结构与i型笼形物水合物的结构相对应，Sr原子填充由Ga和Ge原子形成的“笼”。对各向异性位移参数进行了细化。封闭在十二面体笼中的Sr(1)原子的均方根值的极限图形是一个球体，而封闭在四面体笼中的Sr(2)原子的均方根值的极限图形是一个扁圆椭球。与其他M8GaxGe46 - x （M=K， Ba或void）结构的笼的尺寸比较表明，一旦结构被填充，(i)四面体笼的尺寸变化很小，（ii）十二面体笼的尺寸仅随着填料尺寸的变化而轻微（可测量）地扩大。从热电学的角度来看，这是一个重要的结果，因为这意味着一旦结构被填满，笼状结构就不会“关闭”。
Crystal structural characterization of the Sr8Ga16Ge30 compound was carried out with the Rietveld refinement method using x-ray powder diffraction data. The structure corresponds to that of the type-I clathrate hydrate, with the Sr atoms filling the “cages” formed by the Ga and Ge atoms. Anisotropic displacement parameters were refined. The limiting figure for rms values of the Sr(1) atoms enclosed in the dodecahedral cages is a sphere, while that for the Sr(2) atoms in the tetrakaidecahedral cages move is an oblate ellipsoid. A comparison of the sizes of the cages in this structure with the ones in other M8GaxGe46−x (M=K, Ba, or void) structures shows that once the structure is filled (i) there is very little variation in size of the tetrakaidecahedral cages and (ii) the dodecahedral cages expand only slightly (measurably) as a function of the filler size. This is an important result from the thermoelectric point of view because it means that once the structure is full, the cages will not “close over” th...